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Phoenix Mars Lander: Entry Descent and Landing

(Ben Cichy)
Phoenix is the first Mars Scout mission.
It's the first mission that's going to try to land near the north pole of Mars.
And it's the first mission that actually going to go try and reach out and touch water on the surface of another planet.

(Lynn Craig)
Where there tends to be water at least on Earth, there tends to be life.
And so it's potentially a place where life could have existed on the planet in the past.

(music)

(Erik Bailey)
The main purpose of EDL is to take a spacecraft that is traveling at 12,500 miles an hour
and bring it to a screeching halt in a soft way, in a very short amount of time.

(music)

(Ben Cichy)
When we enter the martian atmosphere, we're 70 miles above the surface of Mars -
and our lander is safely tucked inside what we call an "aeroshell."

(Erik Bailey)
It looks kind of like an ice cream cone, more or less.

(Ben Cichy)
And on the front of it is this heat shield -- this saucer-looking thing
that has about a half inch of what's essentially cork on the front of it, which is our heat shield.
Now this is really special cork, and this cork is what's going to protect us
from the violent atmospheric entry that we're about to experience.

(Rob Grover)
Friction really starts to build up on the spacecraft, and we use the friction
when it's flying through the atmosphere to our advantage, to slow us down.

(Ben Cichy)
From this point, we're gonna decelerate from 12,500 miles an hour down to 900 miles an hour.

(Erik Bailey)
The outside can get almost as hot as the surface of the Sun.

(Rob Grover)
The temperature of the heat shield will reach 2600 degrees Fahrenheit.

(music)

(Erik Bailey)
But the inside doesn't get very hot: it probably gets about room temperature.

(music)

(Richard Kornfeld)
There is this window of opportunity within which we can deploy the parachute.

(Erik Bailey)
If you fire the chute too early, the parachute itself could fail.
The fabric and the stitching could just pull apart.

(music)

And that would be...bad.

(Ben Cichy)
In the first 15 seconds after we deploy the parachute, we'll decelerate from 900 miles an hour
to a relatively slow 250 miles an hour.
We no longer need the heat shield to protect us from the force of atmospheric entry.
So we jettison the heat shield, exposing for the first time our lander to the atmosphere of Mars.

(Lynn Craig)
After the heat shield has been jettisoned and the legs are deployed,
the next step is to have the radar system begin to detect how far Phoenix really is from the ground.

(Ben Cichy)
We've lost 99 percent of our entry velocity, so we're 99 percent of the way to where we want to be.
But that last one percent -- as it always seems to be -- is the tricky part.

(Erik Bailey)
Now the spacecraft actually has to decide when it's going to get rid of its parachute.

(Ben Cichy)
We separate from the lander going 125 miles an hour, at roughly a kilometer above the surface of Mars -- 3200 feet.
That's like taking two Empire State Buildings and stacking them on top of one another.

(Erik Bailey)
That's when we separate from the backshell, and we're now in freefall.
It's a very scary moment. A lot has happen in a very short amount of time.

(music)

(Lynn Craig)
So it's in a freefall, but it's also trying to use all of its actuators
to make sure that it's in the right position to land.

(Erik Bailey)
And then it has to light up its engines,
right itself, and then slowly slow itself down and touch down on the ground safely.

(music)

(Ben Cichy)
Earth and Mars are so far apart that it takes over 10 minutes for a signal from Mars to get to Earth.
And EDL itself is all over in a matter of seven minutes.
So by the time we even hear from the lander that EDL has started, it'll already be over.

(Erik Bailey)
We have to build large amounts of autonomy into the spacecraft so that it can land itself safely.

(Ben Cichy)
EDL is this immense, technically challenging problem.
It's about getting a spacecraft that's hurtling through deep space,
and using all this bag of tricks to somehow figure out
how to get it down to the surface of Mars at zero miles an hour.
It's this immensely exciting and challenging problem.